1. Field of the Invention
The present invention relates to a hard disk drive (HDD). More particularly, the present invention relates to a flexible printed circuit board through which electrical signals are exchanged between a head stack assembly (HSA) and a main circuit board in an HDD, and to an HDD employing such a flexible printed circuit board.
2. Description of the Related Art
Hard disk drives (HDDs) are used as auxiliary memory devices for computers, MP3 players, mobile phones, and the like to read data stored on a data storage disk or to write new data onto the disk using a head slider. In particular, a magnetic head disposed on a head slider reads data stored on the data or writes new data onto the disk while the head slider floats the magnetic head above the disk. The head slider is attached to a front end of a head stack assembly (HSA), and the HSA is pivotable to move the head slider to a predetermined position over the disk to begin a read or write operation. In this respect, the HSA is electrically connected to a main circuit board by means of a flexible printed circuit board so as to receive signals that control its movement over the disk.
FIG. 1 is a plan view of a conventional flexible printed circuit board 10 used in an HDD.
Referring to FIG. 1, the conventional flexible printed circuit board 10 includes a conductive layer 24 forming a circuit pattern and through which electrical signals are transmitted, a sealing layer 22 insulating and sealing the conductive layer 24, and a metal layer 20 enhancing the rigidity of the flexible printed circuit board 10 at opposite ends thereof. Therefore, the conventional flexible printed circuit board 10 has static regions 15 and 20 consisting of the conductive layer 24, the sealing layer 22, and the metal layer 20, and a dynamic region 12 consisting of the conductive layer 24 and the sealing layer 22. The static region 15 is coupled to an HSA (not shown) so as to communicate with the HSA. The other static region 20 is coupled to a main circuit board (not shown) so as to communicate with the main circuit board. The dynamic region 12 flexes between the static regions 15 and 20 as the HSA is pivoted. Thus, the dynamic region 12 is repeatedly bent and straightened in response to the movement of the HSA.
The repeated bending and straightening of the dynamic region 12 of the flexible printed circuit board 10 causes stress concentrations and fatigue at boundaries i and ii between the dynamic region 12 and each of the static regions 15 and 20. As a result, the sealing layer 22 cracks, and the cracks propagate through the sealing layer 22. Ultimately, the conductive layer 24 is damaged due to the cracking of the sealing layer 22.